Steam the potatoes over boiling water until almost cooked through, about 15 minutes.,Let the potatoes cool, then cut them into 1-inch chunks.,In a large cast-iron skillet, melt the butter in the oil until foamy.,Add the red bell pepper and onion and cook over moderately high heat until just softened, about 5 minutes.,Stir in the potatoes, then cook over moderate heat without stirring until golden and crusty on the bottom, about 5 minutes.,Turn the potatoes and cook, turning occasionally, until golden all over, about 15 minutes longer.,______